The cotton gin was a metaphor for the entire Industrial Revolution.
Farming and planting were never a good way to get rich, prior to 1800. Today, they still aren't, unless you are a huge corporation on the level of Archer Daniels Midland. The family farm is a struggling proposition, and has been for most of recorded history. But during the early-mid 19th century, many enterprising farmers had a unique opportunity to make a jump from small to big.
Cotton doesn't grow well everywhere. It grows well in Mississippi, but not Wisconsin. And while cotton has been in great demand for centuries (It's softer than wool, and it does not itch like wool does; underwear as we know it simply did not exist until cotton became available and affordable), it was difficult to process. You can't sell it until it has been removed from its seed, and cutting it off with a knife was difficult and dangerous. One person could, with hard work, separate a single bag of cotton in a day. Growing cotton was a break-even proposition at best.
In 1793, Eli Whitney saw something odd: A chicken rested against a wire mesh fence, and a cat on the other side of it swiped some of its feathers off. He decided to try something similar with cotton. A Georgia plantation owner invested in his idea. He made a small cotton gin, cranked with one hand, that suddenly made that one bag a day into four or five. Then he built a larger one that a horse had to crank by walking in a circle. Not only was cotton suddenly profitable, but the larger plantations could double their output every ten years.
That's just cotton. Imagine applying this kind of thinking to every other crop, and then to every other kind of industry. And instead of selling their yield at a local farmer's market or country store, they could sell to the Ohio valley, New England, California, Europe and a growing South American market base. And that was how a market society exploded and fortunes were made (but not for everybody involved).